Cooling system and cooling method

ABSTRACT

A cooling system which combines a plurality of refrigeration cycles has a fluctuating cooling capacity. Therefore, a cooling system according to the present invention includes: a first cooling means including a first refrigerant transportation means for circulating a refrigerant that receives heat from an object to be cooled; a second refrigerant transportation means connected to the first refrigerant transportation means, for circulating a diverted refrigerant being a part of the refrigerant; a second cooling means for receiving heat from the refrigerant circulating through the first refrigerant transportation means, and cooling the diverted refrigerant; and a flowrate control means for controlling a flowrate of the diverted refrigerant.

TECHNICAL FIELD

The present invention relates to a cooling system and a cooling method which are used to cool an electronic device or the like, and in particular, to a cooling system and a cooling method which use a phase change of a refrigerant.

BACKGROUND ART

In recent years, along with miniaturization and performance enhancement in an electronic device, a heat generation amount and heat generation density thereof have increased. In order to efficiently cool such an electronic device or the like, it is necessary to adopt a cooling technique being high in cooling capacity. One cooling system being high in cooling capacity is a cooling system using a phase change of a refrigerant.

One example of a cooling system using a phase change of a refrigerant is described in PTL 1. A related refrigeration device described in PTL 1 is a cooling system which combines a vapor compression refrigerator and an adsorption refrigerator.

The related refrigeration device includes an adsorption refrigerator including a first adsorber and a second adsorber, a first vapor compression refrigerator, and a second vapor compression refrigerator.

The first and second vapor compression refrigerators include first and second compressors, first and second condensers (radiators), first and second decompressors, an evaporator, and first and second accumulators. Note that the evaporator of the first and second vapor compression refrigerators is integrated.

Furthermore, the adsorption refrigerator includes the first and second adsorbers, first and second adsorbent heat exchangers, first and second water heat exchangers, an outdoor heat exchanger, and the like.

The related refrigeration device heats an adsorbent in the adsorber in a regeneration state by the first condenser included in the first vapor compression refrigerator, and cools the second condenser of the second vapor compression refrigerator by a cooling action of the adsorber in an adsorption state. The related refrigeration device is configured to then switch, at fixed time intervals, the first adsorber and the second adsorber to the adsorption state, and to the regeneration state in which an adsorbed vapor refrigerant is desorbed and regenerated.

Such a configuration enables reduction of compression in the condenser of the second vapor compression refrigerator, and therefore enables reduction of power (compression work) by the compressor of the second vapor compression refrigerator. Consequently, according to the related refrigeration device, it is contemplated that a satisfactory refrigerating capacity can be obtained with a small amount of power in the refrigeration device which combines the first and second vapor compression refrigerators and the adsorption refrigerator.

In addition, techniques described in PTLs 2 and 3 are known as related techniques.

CITATION LIST Patent Literature

[PTL 1] Japanese Laid-open Patent Publication No. H11-190566 (paragraphs [0005] to [0019], FIG. 1)

[PTL 2] Japanese Laid-open Patent Publication No. 2014-009624

[PTL 3] Japanese Laid-open Patent Publication No. H5-272833

SUMMARY OF INVENTION Technical Problem

As described above, the related refrigeration device described in PTL 1 is configured to cool the condenser included in the second vapor compression refrigerator by the adsorption refrigerator which desorbs the adsorbed refrigerant by use of exhaust heat of the first vapor compression refrigerator. Thus, a cooling capacity of the second vapor compression refrigerator is dependent on cooling capacities of the adsorption refrigerator and the first vapor compression refrigerator. As a result, a cooling capacity of the refrigeration device is not always constant, and fluctuates depending on a ratio of amounts of refrigerants circulating through the first vapor compression refrigerator and the second vapor compression refrigerator, respectively.

Thus, a cooling system which combines a plurality of refrigeration cycles has a problem of a fluctuating cooling capacity.

An object of the present invention is to provide a cooling system and a cooling method which solve the aforementioned problem of a fluctuating cooling capacity of a cooling system which combines a plurality of refrigeration cycles.

Solution to Problem

A cooling system according to the present invention includes: a first cooling means including a first refrigerant transportation means for circulating a refrigerant that receives heat from an object to be cooled; a second refrigerant transportation means connected to the first refrigerant transportation means, for circulating a diverted refrigerant being a part of the refrigerant; a second cooling means for receiving heat from the refrigerant circulating through the first refrigerant transportation means, and cooling the diverted refrigerant; and a flowrate control means for controlling a flowrate of the diverted refrigerant.

A cooling method according to the present invention includes: circulating a refrigerant that receives heat from an object to be cooled; diverting a part of the refrigerant, and circulating the diverted refrigerant; receiving heat from the refrigerant and cooling the diverted refrigerant; and controlling a flowrate of the diverted refrigerant in such a way that a cooling capacity for the object to be cooled is substantially constant.

Advantageous Effects of Invention

According to a cooling system and a cooling method of the present invention, it is possible to suppress fluctuation of a cooling capacity of the cooling system even when the cooling system is configured to combine a plurality of refrigeration cycles.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of a cooling system according to a first exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a cooling system according to a second exemplary embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating another configuration of the cooling system according to the second exemplary embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating yet another configuration of the cooling system according to the second exemplary embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.

First Exemplary Embodiment

FIG. 1 is a schematic diagram illustrating a configuration of a cooling system 100 according to a first exemplary embodiment of the present invention. Dotted arrows in FIG. 1 indicate transfer of heat.

The cooling system 100 according to the present exemplary embodiment includes a first cooling means 110, a second cooling means 120, a second refrigerant transportation means 121, and a flowrate control means 130.

The first cooling means 110 includes a first refrigerant transportation means 111 which circulates a refrigerant that has received heat (H1) from an object to be cooled 10. The second refrigerant transportation means 121 is connected to the first refrigerant transportation means 111, and circulates a diverted refrigerant being some of the refrigerant. The second cooling means 120 receives heat (H2) from the refrigerant circulating through the first refrigerant transportation means 111, and cools the diverted refrigerant (H3). Further, the flowrate control means 130 controls a flowrate of the diverted refrigerant.

Herein, temperature of the diverted refrigerant after being cooled by the second cooling means 120 is dependent not only on a cooling capacity of the second cooling means 120 but also on the flowrate of the diverted refrigerant. It is therefore possible to control the temperature of the diverted refrigerant flowing back to the first refrigerant transportation means 111 through the second refrigerant transportation means 121, by controlling the flowrate of the diverted refrigerant. This enables a cooling capacity of the cooling system 100 to be maintained even when the cooling capacity of the second cooling means 120 has fluctuated.

Thus, according to the cooling system 100 in the present exemplary embodiment, it is possible to inhibit fluctuation of the cooling capacity of the cooling system 100 even when the cooling system 100 is configured to combine a plurality of refrigeration cycles including the first cooling means 110 and the second cooling means 120.

Herein, the first cooling means 110 can have a configuration using a vapor compression refrigeration cycle. In addition, the second cooling means 120 can have a configuration using one of an adsorption refrigeration cycle and an absorption refrigeration cycle.

The flowrate control means 130 can be configured to control the flowrate of the diverted refrigerant in such a way that a temperature difference of the diverted refrigerant before and after being cooled by the second cooling means 120 is substantially constant. Specifically, when a temperature difference of the diverted refrigerant is greater than a predetermined value, the flowrate control means 130 increases the flowrate of the diverted refrigerant. On the contrary, when the temperature difference is smaller than the predetermined value, the flowrate control means 130 can be configured to control in such a way as to decrease the flowrate of the diverted refrigerant. Alternatively, the flowrate control means 130 may be configured to control the flowrate of the diverted refrigerant in such a way that a temperature difference of the diverted refrigerant is within a predetermined range, for example, within a range from 0° C. or more to 5° C. or less. Specifically, the flowrate control means 130 may control in such a way as to increase the flowrate of the diverted refrigerant when the temperature difference of the diverted refrigerant is beyond the predetermined range, and decrease the flowrate of the diverted refrigerant when the temperature difference is within the predetermined range.

Furthermore, the flowrate control means 130 can be a flowrate control valve located within a flow path configured by the first refrigerant transportation means 111. Without being limited thereto, the flowrate control means 130 may be a flowrate control valve located within a flow path configured by the second refrigerant transportation means 121.

Next, a cooling method according to the present exemplary embodiment is described.

In the cooling method according to the present exemplary embodiment, first, a refrigerant that has received heat from an object to be cooled is circulated, some of this refrigerant is diverted, and the diverted refrigerant is circulated. Then, heat is received from the refrigerant, and the diverted refrigerant is cooled. Herein, a flowrate of the diverted refrigerant is controlled in such a way that a cooling capacity for the object to be cooled is substantially constant.

The aforementioned control of the flowrate of the diverted refrigerant can be configured to control the flowrate of the diverted refrigerant in such a way that a temperature difference of the diverted refrigerant at preliminary and subsequent stages of a process for cooling the diverted refrigerant is substantially constant. In this instance, the control of the flowrate may be configured to control in such a way as to increase the flowrate of the diverted refrigerant when a temperature difference is greater than a predetermined value, and decrease the flowrate of the diverted refrigerant when the temperature difference is smaller than the predetermined value.

Furthermore, the aforementioned process for receiving heat from the refrigerant and cooling the diverted refrigerant can be a process for desorbing an adsorbent by receiving heat from the refrigerant, and cooling the diverted refrigerant by evaporating the desorbed adsorbent.

Thus, the cooling method according to the present exemplary embodiment is configured to combine a refrigeration cycle for circulating a refrigerant that has received heat from an object to be cooled, and a refrigeration cycle for receiving heat from the refrigerant and cooling a diverted refrigerant. In addition, as described above, according to the cooling method in the present exemplary embodiment, it is possible to inhibit fluctuation of a cooling capacity even when the cooling method is configured to combine a plurality of such refrigeration cycles.

Second Exemplary Embodiment

Next, a second exemplary embodiment of the present invention is described. FIG. 2 schematically illustrates a configuration of a cooling system 1000 according to the second exemplary embodiment of the present invention. In FIG. 2, solid and dotted arrows indicate flow of a refrigerant, and outline arrows indicate flow of heat, respectively.

The cooling system 1000 according to the present exemplary embodiment includes a first cooling device (first cooling means) 1100, a second cooling device (second cooling means) 1200, a second refrigerant transportation unit (second refrigerant transportation means) 1210, and a flowrate control valve (flowrate control means) 1300.

Herein, the cooling system 1000 according to the present exemplary embodiment has a configuration which combines a plurality of refrigeration cycles having the first cooling device 1100 and the second cooling device 1200. In other words, the cooling system 1000 is an exhaust heat collecting type cooling system in which the second cooling device 1200 further cools an object to be cooled 10 using, as an energy source, heat that the first cooling device 1100 has collected by cooling the object to be cooled 10. Herein, the object to be cooled 10 is, for example, an electronic device such as a server.

The first cooling device 1100 includes an evaporator (evaporation means) 1110, a compressor (compression means) 1120, a condenser (condensation means) 1130, an expansion valve (expansion means) 1140, and a first refrigerant transportation unit (first refrigerant transportation means) 1150, thereby configuring a vapor compression refrigeration cycle.

The evaporator 1110 is configured by a radiator or the like, and generates refrigerant vapor resulting from the refrigerant that has received heat and vaporized. The compressor 1120 generates high-pressure refrigerant vapor by adiabatically compressing the refrigerant vapor. The condenser 1130 condenses the high-pressure refrigerant vapor and generates a high-pressure refrigerant liquid. Further, the expansion valve 1140 generates a low-pressure refrigerant liquid by expanding the high-pressure refrigerant liquid.

The first refrigerant transportation unit 1150 configures a flow path of the refrigerant flowing back to the evaporator 1110 from the evaporator 1110 via the compressor 1120, the condenser 1130, and the expansion valve 1140. The solid arrows in FIG. 2 indicate flow of the refrigerant.

The second cooling device 1200 configures one of an adsorption refrigeration cycle and an absorption refrigeration cycle. In the case described in the present exemplary embodiment, an adsorption refrigerator 1201 including an adsorption refrigeration cycle is used as the second cooling device 1200. The adsorption refrigerator 1201 circulates water or the like as a refrigerant by a pump 1202, and cools warm water by a cooling tower 1203 or the like. The dotted arrows in FIG. 2 indicate flow of water as the refrigerant of the adsorption refrigerator 1201.

The second refrigerant transportation unit 1210 configures a flow path which circulates the diverted refrigerant being some of the refrigerant, from between the evaporator 1110 and the compressor 1120 to between the evaporator 1110 and the expansion valve 1140.

The condenser 1130 exchanges heat between the high-pressure refrigerant vapor flowing in the first refrigerant transportation unit 1150 and a refrigerant on a heat receiving side of the second cooling device 1200. In addition, it is possible to provide a configuration including a heat exchanger (heat exchange means) 1220 which exchanges heat between the diverted refrigerant circulated by the second refrigerant transportation unit 1210 and a refrigerant on a cooling side of the second cooling device 1200.

The flowrate control valve 1300 controls a flowrate of the diverted refrigerant. In the case illustrated in FIG. 2, the flowrate control valve 1300 is located within a flow path configured by the first refrigerant transportation unit 1150. Without being limited thereto, a flowrate control valve 1301 may be configured to be located within a flow path configured by the second refrigerant transportation unit 1210, as illustrated in FIG. 3.

Next, an operation of the cooling system 1000 according to the present exemplary embodiment is described.

Firstly, an operation of the first cooling device 1100 is described. A refrigerant liquid which has flowed into the evaporator 1110 including a radiator or the like vaporizes into refrigerant vapor due to exhaust heat at approximately 40 to 50° C. fed from an object to be cooled 10 such as a server. The refrigerant vapor is adiabatically compressed by the compressor 1120 and thereby rises in pressure, and temperature of the refrigerant vapor rises to approximately 50 to 100° C. In order to use heat of the refrigerant vapor which has risen in temperature in the second cooling device 1200, heat is exchanged between the refrigerant and water by the condenser 1130. Accordingly, heat of the refrigerant transfers to water, warm water at approximately 50 to 100° C. is generated, and temperature of the refrigerant falls. The refrigerant condensed and liquefied by the temperature fall is decreased in pressure by the expansion valve 1140. The refrigerant then again flows into the evaporator 1110.

Secondly, an operation of the second cooling device 1200 is described. Heat transfers to the adsorption refrigerator 1201 via the warm water at approximately 50 to 100° C. that has received heat by the heat exchange in the condenser 1130. The adsorption refrigerator 1201 generates cool water at approximately 5 to 20° C. by using the heat, and cools the diverted refrigerant via the heat exchanger 1220.

The diverted refrigerant cooled by the heat exchanger 1220 is condensed and liquefied, and circulated by the second refrigerant transportation unit 1210. Because the second refrigerant transportation unit 1210 is connected between the evaporator 1110 and the expansion valve 1140, the condensed and liquefied diverted refrigerant flows together with the refrigerant liquid decreased in pressure by the expansion valve 1140, and flows back to the evaporator 1110. Note that as illustrated in FIG. 2, a drive unit (drive means) 1230 such as a pump which circulates the diverted refrigerant may be configured to be provided in a flow path of the diverted refrigerant configured by the second refrigerant transportation unit 1210.

The refrigerant liquid which has flowed back to the evaporator 1110 vaporizes due to exhaust heat from an object to be cooled 10 such as a server. The refrigerant vapor which has vaporized in the evaporator 1110 is diverted to and then flows in the second refrigerant transportation unit 1210 connected between the evaporator 1110 and the compressor 1120, and the first refrigerant transportation unit 1150. The diverted refrigerant circulated by the second refrigerant transportation unit 1210 again flows into the heat exchanger 1220.

Next, an operation of the flowrate control valve 1300 is described.

The flowrate control valve 1300 controls the flowrate of the diverted refrigerant. In other words, the flowrate control valve 1300 adjusts a ratio at which the refrigerant vapor that has been vaporized in the evaporator 1110 is diverted to the first refrigerant transportation unit 1150 and the second refrigerant transportation unit 1210. This makes it possible to adjust an amount of the refrigerant cooled by the condenser 1130 via the compressor 1120 provided in the first cooling device 1100, and an amount of the diverted refrigerant cooled by the second cooling device 1200 via the second refrigerant transportation unit 1210.

Furthermore, the cooling system 1000 may also be configured to include a first temperature gauge 1221 which measures temperature of the diverted refrigerant on an entrance side of the heat exchanger 1220, and a second temperature gauge 1222 which measures temperature of the diverted refrigerant on an exit side. The cooling system 1000 can be configured to then control the flowrate control valve 1300 by use of a before-cooling refrigerant temperature T1 which is a measurement result by the first temperature gauge 1221, and an after-cooling refrigerant temperature T2 which is a measurement result by the second temperature gauge 1222.

A specific example of control of the flowrate control valve 1300 is described below.

When the amount of the diverted refrigerant flowing into the heat exchanger 1220 is insufficient, vapor of the diverted refrigerant which has flowed into the heat exchanger 1220 is further supercooled after condensed and liquefied, and a temperature difference T1−T2 between the before-cooling refrigerant temperature T1 and the after-cooling refrigerant temperature T2 therefore increases. In this case, the flowrate control valve 1300 or the flowrate control valve 1301 is adjusted in such a way that the temperature difference T1−T2 is constant at, for example, 5 degrees.

Specifically, when the temperature difference T1−T2 is 5° C. or more (T1−T2≥5° C.), opening of the flowrate control valve 1300 provided in the first refrigerant transportation unit 1150 illustrated in FIG. 2 is decreased. Alternatively, opening of the flowrate control valve 1301 provided in the second refrigerant transportation unit 1210 illustrated in FIG. 3 is increased. On the other hand, when the temperature difference T1−T2 is less than 5° C. (T1−T2<5° C.), the opening of the flowrate control valve 1300 provided in the first refrigerant transportation unit 1150 illustrated in FIG. 2 is increased. Alternatively, the opening of the flowrate control valve 1301 provided in the second refrigerant transportation unit 1210 illustrated in FIG. 3 is decreased.

By controlling the flowrate control valve 1300 in this manner, it is possible to control the temperature of the diverted refrigerant flowing back to the first refrigerant transportation unit 1150 through the second refrigerant transportation unit 1210. This enables a cooling capacity of the cooling system 1000 to be maintained even when a cooling capacity of the second cooling device 1200 has fluctuated.

As described above, according to the cooling system 1000 in the present exemplary embodiment, it is possible to inhibit fluctuation of the cooling capacity of the cooling system 1000 even when the cooling system 1000 is configured to combine a plurality of refrigeration cycles. In other words, it is possible to inhibit fluctuation of the cooling capacity of the cooling system 1000 even when the cooling system 1000 is configured to combine a plurality of refrigeration cycles including the first cooling device 1100 (vapor compression refrigeration cycle) and the second cooling device 1200 (adsorption refrigeration cycle).

In addition, as illustrated in FIG. 4, the heat exchanger 1220 can be configured to be located higher than the evaporator 1110. Such a configuration enables the diverted refrigerant to flow in the second refrigerant transportation unit 1210 and flow back to the evaporator 1110 due to a gravitational action. Thus, the aforementioned drive unit (drive means) which is a pump or the like becomes unnecessary.

The present invention has been described above with the above exemplary embodiments as exemplars. However, the present invention is not limited to the above exemplary embodiments. In other words, various aspects that can be appreciated by a person skilled in the art are applicable to the present invention within the scope of the present invention.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2015-188225, filed on Sep. 25, 2015, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   100 Cooling system -   110 First cooling means -   111 First refrigerant transportation means -   120 Second cooling means -   121 Second refrigerant transportation means -   130 Flowrate control means -   1000 Cooling system -   1100 First cooling device -   1110 Evaporator -   1120 Compressor -   1130 Condenser -   1140 Expansion valve -   1150 First refrigerant transportation unit -   1200 Second cooling device -   1201 Adsorption refrigerator -   1202 Pump -   1203 Cooling tower -   1210 Second refrigerant transportation unit -   1220 Heat exchanger -   1221 First temperature gauge -   1222 Second temperature gauge -   1230 Drive unit -   1300, 1301 Flowrate control valve -   10 Object to be cooled 

1. A cooling system comprising: a first cooling unit including a first refrigerant transportation unit circulating a refrigerant that receives heat from an object to be cooled; a second refrigerant transportation unit connected to the first refrigerant transportation unit, circulating a diverted refrigerant being a part of the refrigerant; a second cooling unit receiving heat from the refrigerant circulating through the first refrigerant transportation unit, and cooling the diverted refrigerant; and a flowrate control unit controlling a flowrate of the diverted refrigerant.
 2. The cooling system according to claim 1, wherein the flowrate control unit is a flowrate control valve located within a flow path configured by the first refrigerant transportation unit.
 3. The cooling system according to claim 1, wherein the flowrate control unit is a flowrate control valve located within a flow path configured by the second refrigerant transportation unit.
 4. The cooling system according to claim 1, wherein the flowrate control unit controls a flowrate of the diverted refrigerant in such a way that a temperature difference of the diverted refrigerant before and after being cooled by the second cooling unit is within a predetermined range.
 5. The cooling system according to claim 4, wherein the flowrate control unit increases a flowrate of the diverted refrigerant when the temperature difference is beyond the predetermined range, and decreases a flowrate of the diverted refrigerant when the temperature difference is within the predetermined range.
 6. The cooling system according to claim 1, wherein the first cooling unit configures a vapor compression refrigeration cycle, and includes an evaporation unit generating refrigerant vapor resulting from the refrigerant that receives heat and is vaporized, a compression unit generating high-pressure refrigerant vapor by compressing the refrigerant vapor, a condensation unit condensing the high-pressure refrigerant vapor and generating high-pressure refrigerant liquid, and an expansion unit generating low-pressure refrigerant liquid by expanding the high-pressure refrigerant liquid, the first refrigerant transportation unit configures a flow path of the refrigerant flowing back to the evaporation unit from the evaporation unit via the compression unit, the condensation unit, and the expansion unit, and the second refrigerant transportation unit configures a flow path which circulates the diverted refrigerant from between the evaporation unit and the compression unit to between the evaporation unit and the expansion unit.
 7. The cooling system according to claim 6, further comprising a heat exchange unit exchanging heat between the diverted refrigerant and a refrigerant on a cooling side of the second cooling unit, wherein the condensation unit exchanges heat between the high-pressure refrigerant vapor and a refrigerant on a heat receiving side of the second cooling unit.
 8. The cooling system according to claim 7, wherein the heat exchange unit is located above the evaporation unit.
 9. The cooling system according to claim 1, wherein the second cooling unit configures one of an adsorption refrigeration cycle and an absorption refrigeration cycle.
 10. The cooling system according to claim 1, further comprising: a drive unit circulating the diverted refrigerant in a flow path of the diverted refrigerant configured by the second refrigerant transportation unit.
 11. A cooling method comprising: circulating a refrigerant that receives heat from an object to be cooled; diverting a part of the refrigerant, and circulating the diverted refrigerant; receiving heat from the refrigerant and cooling the diverted refrigerant; and controlling a flowrate of the diverted refrigerant in such a way that a cooling capacity for the object to be cooled is substantially constant.
 12. The cooling method according to claim 11, further comprising controlling a flowrate of the diverted refrigerant in such a way that a temperature difference of the diverted refrigerant at preliminary and subsequent stages of a process of cooling the diverted refrigerant is substantially constant.
 13. The cooling method according to claim 12, further comprising: increasing a flowrate of the diverted refrigerant when the temperature difference is greater than a predetermined value; and decreasing a flowrate of the diverted refrigerant when the temperature difference is smaller than a predetermined value.
 14. The cooling method according to claim 11, further comprising desorbing an adsorbent by receiving heat from the refrigerant, and cooling the diverted refrigerant by evaporating the desorbed adsorbent. 